Field of Invention
This invention relates generally to a power supply and a power supply apparatus, and particularly to switching power supplies and a power supply apparatus using the switching power supplies.
Related Art
With the increasing network bandwidth, the so-called cloud computing is gaining more popularity. As a result, more data centers are built, and the size of each data center becomes larger. As the scale of the data centers increases, the demand for energy rises, and so is the demand for more switching power supplies. In addition, in order to provide higher power, it is often practical to connect multiple switching power supplies in parallel, instead of using a single power supply with a large power output.
However, due to precision limitations in the manufacture process, there can still exist slight difference in output voltages even for two switching power supplies with the same specification. FIG. 1 provides an illustrative view of a conventional parallel usage of two switching power supplies. In FIG. 1, two switching power supplies 100 and 100′ are connected in parallel to provide power to the same load 10. The switching power supply 100 and the switching power supply 100′ may, for example, have the same rated output voltage and the same output power. Thus, the switching power supply 100 and the switching power supply 100′ shall theoretically evenly provide the power to the same load 10. However, due to their manufacturing process, the switching power supply 100 and the switching power supply 100′ may have different reference voltages. This will cause their output voltages to be different. For example, if the switching power supply 100 has a smaller reference voltage than the reference voltage of the switching power supply 100′, when the switching power supply 100 and the switching power supply 100′ are connected to the same load 10, the feedback circuit of the switching power supply 100′ will detect a voltage that is always higher than the reference voltage of the switching power supply 100′ itself. This will cause the switching power supply 100′ not to actively function, and now the power is supplied entirely from the switching power supply 100. As a result, the power required by the load 10 cannot be shared evenly between the switching power supply 100 and the switching power supply 100′.
In addition, multiple power supplies in a data center will be stacked in a rack. Because hot air will rise above, the upper switching power supplies will operate at higher temperature than the lower ones. This may result in the shortness of machine life for the upper switching power supplies. In this case, the user may increase the usage rate for the lower switching power supplies and decrease the usage rate for the upper ones to achieve consistent heat loss and to prolong the life cycle of the switching power supplies.
To achieve this goal, the current solution is to use signal lines and current share bus to connect each switching power supply to adjust its usage rate. However, this will cause the circuitry to be very complex, and the signals lines will be easily subject to environmental interference, which will in turn lead to system instability.
In addition, carbon reduction is becoming the current trend, and a growing number of data centers or manufacturing plants have begun to use renewable energy sources like solar panels or wind turbines to contribute to environmental conservation. However, due to the weather conditions, the power supplied from the renewable energy sources is often not stable or sufficient, so most of the data centers or manufacturing plants will not rely solely on renewable energy sources, but will combine them with the electricity provided by the public power plants. When combining these different power sources, they will need to work with different switching power supplies with different reference voltages—causing them unable to be combined in parallel. Thus, the power from the renewable energy sources are often instead stored in batteries, which will in turn be used to provide power to the data centers. Unfortunately, the process of storing these power to batteries and extracting the power from them is often inefficient.